Optical imaging lens

ABSTRACT

An optical imaging lens includes a first lens element, a second lens element, a third lens element and a fourth lens element. The first lens element has positive refracting power, an optical-axis region of the object-side surface of the second lens element is convex, a periphery region of the object-side surface of the second lens element is convex, and an optical-axis region of the image-side surface of the second lens element is convex. The Abbe number of the first lens element is ν1, the Abbe number of the second lens element is ν2 and the Abbe number of the third lens element is ν3 to satisfy 61.119≤ν1+ν2+ν3≤96.733.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of the application Ser. No.15/880,551, filed on Jan. 26, 2018, which claims priority to ChinesePatent Application No. 201711477746.1, filed on Dec. 29, 2017. Thecontents thereof are included herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention generally relates to an optical imaging lens.Specifically speaking, the present invention is directed to an opticalimaging lens for use in portable electronic devices such as mobilephones, cameras, tablet personal computers, or personal digitalassistants (PDA) for taking pictures and for recording videos, and foruse in the field of detection of 3D images.

2. Description of the Prior Art

In recent years, the optical imaging lenses evolve and the applicationis getting wider and wider. In addition to being lighter, thinner,shorter and smaller, it is better to increase the luminous flux with thedesign of a smaller f-number. Accordingly, it is an important objectiveto develop an optical imaging lens not only to be lighter, thinner,shorter and smaller at the same time but also to have an optical imaginglens with a small f-number and with good imaging quality.

SUMMARY OF THE INVENTION

In light of the above, an embodiment of the present invention proposesan optical imaging lens of four lens elements which has reduced opticalimaging lens system length, ensured imaging quality, a smaller f-number,good optical performance and is technically possible. The opticalimaging lens of four lens elements of the present invention from anobject side to an image side in order along an optical axis has a firstlens element, a second lens element, a third lens element and a fourthlens element. Each one of the first lens element, the second lenselement, the third lens element and the fourth lens element respectivelyhas an object-side surface which faces toward the object side to allowimaging rays to pass through as well as an image-side surface whichfaces toward the image side to allow the imaging rays to pass through.

In one embodiment of the present invention, the optical-axis region ofthe image-side surface of the first lens element is concave. Theperiphery region of the image-side surface of the second lens element isconvex. The third lens has positive refracting power and theoptical-axis region of the object-side surface of the fourth lenselement is convex. Lens elements having refracting power included by theoptical imaging lens are only the four lens elements described above.The Abbe number of the first lens element is ν1, the Abbe number of thesecond lens element is ν2, the Abbe number of the third lens element isν3 and the Abbe number of the fourth lens element is ν4 to satisfyν2≤30.000 and (ν1+ν3+ν4)≤120.000.

In the optical imaging lens of the present invention, the embodimentsfurther satisfy the following relationships:

ALT/BFL≥1.200;

AAG/G23≤2.200;

EFL/(T1+T3)≤3.500;

(T2+T3)/T1≥1.800;

(T3+T4)/(G23+G34)≤3.500;

(T1+T2)/(G12+G23)≤2.800;

BFL/(G34+T4)≤3.100;

TL/(T1+G12)≥3.200;

EFL/AAG≤3.900;

TTL/(T3+T4)≥3.800;

ALT/T2≤4.800;

(T4+BFL)/T3≤4.500;

T2/T1≥1.000;

ALT/AAG≤4.500;

TL/BFL≥1.800;

(T2+T3+T4)/T1≥2.500;

(T1+T3+T4)/T2≤3.500;

EFL/(T2+G23)≤3.000; and

ALT/T1≥3.500.

T1 is a thickness of the first lens element along the optical axis, T2is a thickness of the second lens element along the optical axis, T3 isa thickness of the third lens element along the optical axis, T4 is athickness of the fourth lens element along the optical axis, G12 is anair gap between the first lens element and the second lens element alongthe optical axis, G23 is an air gap between the second lens element andthe third lens element along the optical axis, G34 is an air gap betweenthe third lens element and the fourth lens element along the opticalaxis.

TTL is a distance from the object-side surface of the first lens elementto an image plane along the optical axis, TL is a distance from theobject-side surface of the first lens element to the image-side surfaceof the fourth lens element along the optical axis, ALT is a sum ofthickness of all the four lens elements along the optical axis, AAG is asum of three air gaps from the first lens element to the fourth lenselement along the optical axis, EFL is an effective focal length of theoptical imaging lens and BFL is a distance from the image-side surfaceof the fourth lens element to an image plane along the optical axis.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-5 illustrate the methods for determining the surface shapes andfor determining an optical axis region and a periphery region of onelens element.

FIG. 6 illustrates a first embodiment of the optical imaging lens of thepresent invention.

FIG. 7A illustrates the longitudinal spherical aberration on the imageplane of the first embodiment.

FIG. 7B illustrates the field curvature on the sagittal direction of thefirst embodiment.

FIG. 7C illustrates the field curvature on the tangential direction ofthe first embodiment.

FIG. 7D illustrates the distortion of the first embodiment.

FIG. 8 illustrates a second embodiment of the optical imaging lens ofthe present invention.

FIG. 9A illustrates the longitudinal spherical aberration on the imageplane of the second embodiment.

FIG. 9B illustrates the field curvature on the sagittal direction of thesecond embodiment.

FIG. 9C illustrates the field curvature on the tangential direction ofthe second embodiment.

FIG. 9D illustrates the distortion of the second embodiment.

FIG. 10 illustrates a third embodiment of the optical imaging lens ofthe present invention.

FIG. 11A illustrates the longitudinal spherical aberration on the imageplane of the third embodiment.

FIG. 11B illustrates the field curvature on the sagittal direction ofthe third embodiment.

FIG. 11C illustrates the field curvature on the tangential direction ofthe third embodiment.

FIG. 11D illustrates the distortion of the third embodiment.

FIG. 12 illustrates a fourth embodiment of the optical imaging lens ofthe present invention.

FIG. 13A illustrates the longitudinal spherical aberration on the imageplane of the fourth embodiment.

FIG. 13B illustrates the field curvature on the sagittal direction ofthe fourth embodiment.

FIG. 13C illustrates the field curvature on the tangential direction ofthe fourth embodiment.

FIG. 13D illustrates the distortion of the fourth embodiment.

FIG. 14 illustrates a fifth embodiment of the optical imaging lens ofthe present invention.

FIG. 15A illustrates the longitudinal spherical aberration on the imageplane of the fifth embodiment.

FIG. 15B illustrates the field curvature on the sagittal direction ofthe fifth embodiment.

FIG. 15C illustrates the field curvature on the tangential direction ofthe fifth embodiment.

FIG. 15D illustrates the distortion of the fifth embodiment.

FIG. 16 illustrates a sixth embodiment of the optical imaging lens ofthe present invention.

FIG. 17A illustrates the longitudinal spherical aberration on the imageplane of the sixth embodiment.

FIG. 17B illustrates the field curvature on the sagittal direction ofthe sixth embodiment.

FIG. 17C illustrates the field curvature on the tangential direction ofthe sixth embodiment.

FIG. 17D illustrates the distortion of the sixth embodiment.

FIG. 18 illustrates a seventh embodiment of the optical imaging lens ofthe present invention.

FIG. 19A illustrates the longitudinal spherical aberration on the imageplane of the seventh embodiment.

FIG. 19B illustrates the field curvature on the sagittal direction ofthe seventh embodiment.

FIG. 19C illustrates the field curvature on the tangential direction ofthe seventh embodiment.

FIG. 19D illustrates the distortion of the seventh embodiment.

FIG. 20 shows the optical data of the first embodiment of the opticalimaging lens.

FIG. 21 shows the aspheric surface data of the first embodiment.

FIG. 22 shows the optical data of the second embodiment of the opticalimaging lens.

FIG. 23 shows the aspheric surface data of the second embodiment.

FIG. 24 shows the optical data of the third embodiment of the opticalimaging lens.

FIG. 25 shows the aspheric surface data of the third embodiment.

FIG. 26 shows the optical data of the fourth embodiment of the opticalimaging lens.

FIG. 27 shows the aspheric surface data of the fourth embodiment.

FIG. 28 shows the optical data of the fifth embodiment of the opticalimaging lens.

FIG. 29 shows the aspheric surface data of the fifth embodiment.

FIG. 30 shows the optical data of the sixth embodiment of the opticalimaging lens.

FIG. 31 shows the aspheric surface data of the sixth embodiment.

FIG. 32 shows the optical data of the seventh embodiment of the opticalimaging lens.

FIG. 33 shows the aspheric surface data of the seventh embodiment.

FIG. 34 shows some important ratios in the embodiments.

FIG. 35 shows some important ratios in the embodiments.

DETAILED DESCRIPTION

In the present disclosure, the optical system may comprise at least onelens element to receive imaging rays that are incident on the opticalsystem over a set of angles ranging from parallel to an optical axis toa half field of view (HFOV) angle with respect to the optical axis. Theimaging rays pass through the optical system to produce an image on animage plane. The term “a lens element having positive refracting power(or negative refracting power)” means that the paraxial refracting powerof the lens element in Gaussian optics is positive (or negative). Theterm “an object-side (or image-side) surface of a lens element” refersto a specific region of that surface of the lens element at whichimaging rays can pass through that specific region. Imaging rays includeat least two types of rays: a chief ray Lc and a marginal ray Lm (asshown in FIG. 1). An object-side (or image-side) surface of a lenselement can be characterized as having several regions, including anoptical axis region, a periphery region, and, in some cases, one or moreintermediate regions, as discussed more fully below.

FIG. 1 is a radial cross-sectional view of a lens element 100. Tworeferential points for the surfaces of the lens element 100 can bedefined: a central point, and a transition point. The central point of asurface of a lens element is a point of intersection of that surface andthe optical axis I. As illustrated in FIG. 1, a first central point CP1may be present on the object-side surface 110 of lens element 100 and asecond central point CP2 may be present on the image-side surface 120 ofthe lens element 100. The transition point is a point on a surface of alens element, at which the line tangent to that point is perpendicularto the optical axis I. The optical boundary OB of a surface of the lenselement is defined as a point at which the radially outermost marginalray Lm passing through the surface of the lens element intersects thesurface of the lens element. All transition points lie between theoptical axis I and the optical boundary OB of the surface of the lenselement. If multiple transition points are present on a single surface,then these transition points are sequentially named along the radialdirection of the surface with reference numerals starting from the firsttransition point. For example, the first transition point, e.g., TP1,(closest to the optical axis I), the second transition point, e.g., TP2,(as shown in FIG. 4), and the Nth transition point (farthest from theoptical axis I).

The region of a surface of the lens element from the central point tothe first transition point TP1 is defined as the optical axis region,which includes the central point. The region located radially outside ofthe farthest Nth transition point from the optical axis I to the opticalboundary OB of the surface of the lens element is defined as theperiphery region. In some embodiments, there may be intermediate regionspresent between the optical axis region and the periphery region, withthe number of intermediate regions depending on the number of thetransition points.

The shape of a region is convex if a collimated ray being parallel tothe optical axis I and passing through the region is bent toward theoptical axis I such that the ray intersects the optical axis I on theimage side A2 of the lens element. The shape of a region is concave ifthe extension line of a collimated ray being parallel to the opticalaxis I and passing through the region intersects the optical axis I onthe object side A1 of the lens element.

Additionally, referring to FIG. 1, the lens element 100 may also have amounting portion 130 extending radially outward from the opticalboundary OB. The mounting portion 130 is typically used to physicallysecure the lens element to a corresponding element of the optical system(not shown). Imaging rays do not reach the mounting portion 130. Thestructure and shape of the mounting portion 130 are only examples toexplain the technologies, and should not be taken as limiting the scopeof the present disclosure. The mounting portion 130 of the lens elementsdiscussed below may be partially or completely omitted in the followingdrawings.

Referring to FIG. 2, optical axis region Z1 is defined between centralpoint CP and first transition point TP1. Periphery region Z2 is definedbetween TP1 and the optical boundary OB of the surface of the lenselement. Collimated ray 211 intersects the optical axis I on the imageside A2 of lens element 200 after passing through optical axis regionZ1, i.e., the focal point of collimated ray 211 after passing throughoptical axis region Z1 is on the image side A2 of the lens element 200at point R in FIG. 2. Accordingly, since the ray itself intersects theoptical axis I on the image side A2 of the lens element 200, opticalaxis region Z1 is convex. On the contrary, collimated ray 212 divergesafter passing through periphery region Z2. The extension line EL ofcollimated ray 212 after passing through periphery region Z2 intersectsthe optical axis I on the object side A1 of lens element 200, i.e., thefocal point of collimated ray 212 after passing through periphery regionZ2 is on the object side A1 at point M in FIG. 2. Accordingly, since theextension line EL of the ray intersects the optical axis I on the objectside A1 of the lens element 200, periphery region Z2 is concave. In thelens element 200 illustrated in FIG. 2, the first transition point TP1is the border of the optical axis region and the periphery region, i.e.,TP1 is the point at which the shape changes from convex to concave.

Alternatively, there is another way for a person having ordinary skillin the art to determine whether an optical axis region is convex orconcave by referring to the sign of “Radius” (the “R” value), which isthe paraxial radius of shape of a lens surface in the optical axisregion. The R value is commonly used in conventional optical designsoftware such as Zemax and CodeV. The R value usually appears in thelens data sheet in the software. For an object-side surface, a positiveR value defines that the optical axis region of the object-side surfaceis convex, and a negative R value defines that the optical axis regionof the object-side surface is concave. Conversely, for an image-sidesurface, a positive R value defines that the optical axis region of theimage-side surface is concave, and a negative R value defines that theoptical axis region of the image-side surface is convex. The resultfound by using this method should be consistent with the methodutilizing intersection of the optical axis by rays/extension linesmentioned above, which determines surface shape by referring to whetherthe focal point of a collimated ray being parallel to the optical axis Iis on the object-side or the image-side of a lens element. As usedherein, the terms “a shape of a region is convex (concave),” “a regionis convex (concave),” and “a convex- (concave-) region,” can be usedalternatively.

FIG. 3, FIG. 4 and FIG. 5 illustrate examples of determining the shapeof lens element regions and the boundaries of regions under variouscircumstances, including the optical axis region, the periphery region,and intermediate regions as set forth in the present specification.

FIG. 3 is a radial cross-sectional view of a lens element 300. Asillustrated in FIG. 3, only one transition point TP1 appears within theoptical boundary OB of the image-side surface 320 of the lens element300. Optical axis region Z1 and periphery region Z2 of the image-sidesurface 320 of lens element 300 are illustrated. The R value of theimage-side surface 320 is positive (i.e., R>0). Accordingly, the opticalaxis region Z1 is concave.

In general, the shape of each region demarcated by the transition pointwill have an opposite shape to the shape of the adjacent region(s).Accordingly, the transition point will define a transition in shape,changing from concave to convex at the transition point or changing fromconvex to concave. In FIG. 3, since the shape of the optical axis regionZ1 is concave, the shape of the periphery region Z2 will be convex asthe shape changes at the transition point TP1.

FIG. 4 is a radial cross-sectional view of a lens element 400. Referringto FIG. 4, a first transition point TP1 and a second transition pointTP2 are present on the object-side surface 410 of lens element 400. Theoptical axis region Z1 of the object-side surface 410 is defined betweenthe optical axis I and the first transition point TP1. The R value ofthe object-side surface 410 is positive (i.e., R>0). Accordingly, theoptical axis region Z1 is convex.

The periphery region Z2 of the object-side surface 410, which is alsoconvex, is defined between the second transition point TP2 and theoptical boundary OB of the object-side surface 410 of the lens element400. Further, intermediate region Z3 of the object-side surface 410,which is concave, is defined between the first transition point TP1 andthe second transition point TP2. Referring once again to FIG. 4, theobject-side surface 410 includes an optical axis region Z1 locatedbetween the optical axis I and the first transition point TP1, anintermediate region Z3 located between the first transition point TP1and the second transition point TP2, and a periphery region Z2 locatedbetween the second transition point TP2 and the optical boundary OB ofthe object-side surface 410. Since the shape of the optical axis regionZ1 is designed to be convex, the shape of the intermediate region Z3 isconcave as the shape of the intermediate region Z3 changes at the firsttransition point TP1, and the shape of the periphery region Z2 is convexas the shape of the periphery region Z2 changes at the second transitionpoint TP2.

FIG. 5 is a radial cross-sectional view of a lens element 500. Lenselement 500 has no transition point on the object-side surface 510 ofthe lens element 500. For a surface of a lens element with no transitionpoint, for example, the object-side surface 510 the lens element 500,the optical axis region Z1 is defined as the region between 0-50% of thedistance between the optical axis I and the optical boundary OB of thesurface of the lens element and the periphery region is defined as theregion between 50%-100% of the distance between the optical axis I andthe optical boundary OB of the surface of the lens element. Referring tolens element 500 illustrated in FIG. 5, the optical axis region Z1 ofthe object-side surface 510 is defined between the optical axis I and50% of the distance between the optical axis I and the optical boundaryOB. The R value of the object-side surface 510 is positive (i.e., R>0).Accordingly, the optical axis region Z1 is convex. For the object-sidesurface 510 of the lens element 500, because there is no transitionpoint, the periphery region Z2 of the object-side surface 510 is alsoconvex. It should be noted that lens element 500 may have a mountingportion (not shown) extending radially outward from the periphery regionZ2.

As shown in FIG. 6, the optical imaging lens 1 of four lens elements ofthe present invention, sequentially located from an object side 2 (wherean object is located) to an image side 3 along an optical axis 4, has afirst lens element 10, an aperture stop (ape. stop) 80, a second lenselement 20, a third lens element 30, a fourth lens element 40 and animage plane 71. Generally speaking, the first lens element 10, thesecond lens element 20, the third lens element 30 and the fourth lenselement 40 may be made of a transparent plastic material but the presentinvention is not limited to this. Each lens element has an appropriaterefracting power. In the present invention, the lens elements havingrefracting power included by the optical imaging lens 1 are only thefour lens elements as described above. The optical axis 4 is the opticalaxis of the entire optical imaging lens 1, and the optical axis 4 ofeach of the lens elements coincides with the optical axis 4 of theoptical imaging lens 1.

Furthermore, the optical imaging lens 1 includes an aperture stop (ape.stop) 80 disposed in an appropriate position. In FIG. 6, the aperturestop 80 is disposed between the first lens element 10 and the secondlens element 20. When light emitted or reflected by an object (notshown) which is located at the object side 2 enters the optical imaginglens 1 of the present invention, it forms a clear and sharp image on theimage plane 71 at the image side 3 after passing through the first lenselement 10, the aperture stop 80, the second lens element 20, the thirdlens element 30, the fourth lens element 40 and the optional filter 70.In the embodiments of the present invention, the optional setting filter70 is disposed between the image-side surface 42 of the fourth lenselement 40 and the image plane 71. In one embodiment of the presentinvention, the optional setting filter 70 may be a filter of varioussuitable functions, for example, the filter 70 may be a filter to allowlight of specific wavelength (such as IR or visible light) to passthrough.

Each lens element in the optical imaging lens 1 of the present inventionhas an object-side surface facing toward the object side 2 and allowingimaging rays to pass through as well as an image-side surface facingtoward the image side 3 and allowing the imaging rays to pass through.In addition, each object-side surface and image-side surface in theoptical imaging lens 1 of the present invention has an optical axisregion and a periphery region. For example, the first lens element 10has an object-side surface 11 and an image-side surface 12; the secondlens element 20 has an object-side surface 21 and an image-side surface22; the third lens element 30 has an object-side surface 31 and animage-side surface 32; the fourth lens element 40 has an object-sidesurface 41 and an image-side surface 42.

Each lens element in the optical imaging lens 1 of the present inventionfurther has a thickness T along the optical axis 4. For example, thefirst lens element 10 has a first lens element thickness T1, the secondlens element 20 has a second lens element thickness T2, the third lenselement 30 has a third lens element thickness T3, the fourth lenselement 40 has a fourth lens element thickness T4. Therefore, the sum ofthe thickness of all the four lens elements in the optical imaging lens1 along the optical axis 4 is ALT=T1+T2+T3+T4.

In addition, between two adjacent lens elements in the optical imaginglens 1 of the present invention there may be an air gap along theoptical axis 4. For example, there is an air gap G12 disposed betweenthe first lens element 10 and the second lens element 20, an air gap G23disposed between the second lens element 20 and the third lens element30, an air gap G34 disposed between the third lens element 30 and thefourth lens element 40. Therefore, the sum of three air gaps from thefirst lens element 10 to the fourth lens element 40 along the opticalaxis 4 is AAG=G12+G23+G34.

In addition, the distance from the object-side surface 11 of the firstlens element 10 to the image plane 71, namely the total length of theoptical imaging lens along the optical axis 4 is TTL; the effectivefocal length of the optical imaging lens is EFL; the distance from theimage-side surface 42 of fourth lens element 40 to the image plane 71along the optical axis 4 is BFL; the distance from the object-sidesurface 11 of the first lens element 10 to the image-side surface 42 ofthe fourth lens element 40 along the optical axis 4 is TL.

When the filter 70 is disposed between the fourth lens element 40 andthe image plane 71, the distance from the image-side surface 42 of thefourth lens element 40 to the filter 70 along the optical axis 4 is G4F;the thickness of the filter 70 along the optical axis 4 is TF; thedistance from the filter 70 to the image plane 71 along the optical axis4 is GFP; and the distance from the image-side surface 42 of the fourthlens element 40 to the image plane 71 along the optical axis 4 is BFL.Therefore, BFL=G4F+TF+GFP.

Furthermore, the focal length of the first lens element 10 is f1; thefocal length of the second lens element 20 is f2; the focal length ofthe third lens element 30 is f3; the focal length of the fourth lenselement 40 is f4; the refractive index of the first lens element 10 isn1; the refractive index of the second lens element 20 is n2; therefractive index of the third lens element 30 is n3; the refractiveindex of the fourth lens element 40 is n4; the Abbe number of the firstlens element 10 is ν1; the Abbe number of the second lens element 20 isν2; the Abbe number of the third lens element 30 is ν3; and the Abbenumber of the fourth lens element 40 is ν4.

First Embodiment

Please refer to FIG. 6 which illustrates the first embodiment of theoptical imaging lens 1 of the present invention. Please refer to FIG. 7Afor the longitudinal spherical aberration on the image plane 71 of thefirst embodiment; please refer to FIG. 7B for the field curvature on thesagittal direction; please refer to FIG. 7C for the field curvature onthe tangential direction; and please refer to FIG. 7D for the distortionaberration. The Y axis of the spherical aberration in each embodiment is“field of view” for 1.0. The Y axis of the field curvature and thedistortion aberration in each embodiment stands for “image height”, IMH,which is 1.500 mm.

The optical imaging lens 1 of the first embodiment exclusively has fourlens elements 10, 20, 30 and 40 with refracting power. The opticalimaging lens 1 also has an aperture stop 80 and an image plane 71. Theaperture stop 80 is provided between the first lens element 10 and thesecond lens element 20.

The first lens element 10 has negative refracting power. An optical axisregion 13 of the object-side surface 11 facing toward the object side 2is convex, and a periphery region 14 of the object-side surface 11facing toward the object side 2 is convex. An optical axis region 16 ofthe image-side surface 12 facing toward the image side 3 is concave, anda periphery region 17 of the image-side surface 12 facing toward theimage side 3 is concave. Besides, both the object-side surface 11 andthe image-side 12 of the first lens element 10 are aspherical surfacesbut the present invention are not limited to these.

The second lens element 20 has positive refracting power. An opticalaxis region 23 of the object-side surface 21 facing toward the objectside 2 is convex, and a periphery region 24 of the object-side surface21 facing toward the object side 2 is convex. An optical axis region 26of the image-side surface 22 facing toward the image side 3 is convex,and a periphery region 27 of the image-side surface 22 facing toward theimage side 3 is convex. Besides, both the object-side surface 21 and theimage-side 22 of the second lens element 20 are aspherical surfaces butthe present invention are not limited to these.

The third lens element 30 has positive refracting power. An optical axisregion 33 of the object-side surface 31 facing toward the object side 2is concave, and a periphery region 34 of the object-side surface 31facing toward the object side 2 is concave. An optical axis region 36 ofthe image-side surface 32 facing toward the image side 3 is convex, anda periphery region 37 of the image-side surface 32 facing toward theimage side 3 is convex. Besides, both the object-side surface 31 and theimage-side 32 of the third lens element 30 are aspherical surfaces butthe present invention are not limited to these.

The fourth lens element 40 has positive refracting power. An opticalaxis region 43 of the object-side surface 41 facing toward the objectside 2 is convex, and a periphery region 44 of the object-side surface41 facing toward the object side 2 is concave. An optical axis region 46of the image-side surface 42 facing toward the image side 3 is concave,and a periphery region 47 of the image-side surface 42 facing toward theimage side 3 is convex. Besides, both the object-side surface 41 and theimage-side 42 of the fourth lens element 40 are aspherical surfaces butthe present invention are not limited to these.

In the first lens element 10, the second lens element 20, the third lenselement 30 and the fourth lens element 40 of the optical imaging lenselement 1 of the present invention, there are 8 surfaces, such as theobject-side surfaces 11/21/31/41 and the image-side surfaces12/22/32/42. If a surface is aspherical, these aspheric coefficients aredefined according to the following formula:

${Z(Y)} = {{\frac{Y^{2}}{R}/( {1 + \sqrt{1 - {( {1 + K} )\frac{Y^{2}}{R^{2}}}}} )} + {\sum\limits_{i = 1}^{n}\;{a_{2i} \times Y^{2i}}}}$

In which:

R represents the curvature radius of the lens element surface;

Z represents the depth of an aspherical surface (the perpendiculardistance between the point of the aspherical surface at a distance Yfrom the optical axis and the tangent plane of the vertex on the opticalaxis of the aspherical surface);

Y represents a vertical distance from a point on the aspherical surfaceto the optical axis;

K is a conic constant; and

a_(2i) is the aspheric coefficient of the 2i^(th) order.

The optical data of the first embodiment of the optical imaging lens 1are shown in FIG. 20 while the aspheric surface data are shown in FIG.21. In the present embodiments of the optical imaging lens, the f-numberof the entire optical imaging lens element system is Fno, EFL is theeffective focal length, HFOV stands for the half field of view which ishalf of the field of view of the entire optical imaging lens elementsystem, and the unit for the curvature radius, the thickness and thefocal length is in millimeters (mm). In this embodiment, imageheight=1.500 mm; EFL=2.108 mm; HFOV=34.216 degrees; TTL=3.272 mm;Fno=1.5.

Second Embodiment

Please refer to FIG. 8 which illustrates the second embodiment of theoptical imaging lens 1 of the present invention. It is noted that fromthe second embodiment to the following embodiments, in order to simplifythe figures, only the components different from what the firstembodiment has, and the basic lens elements will be labeled in figures.Other components that are the same as what the first embodiment has,such as the object-side surface, the image-side surface, the opticalaxis region and the periphery region will be omitted in the followingembodiments. Please refer to FIG. 9A for the longitudinal sphericalaberration on the image plane 71 of the second embodiment, please referto FIG. 9B for the field curvature on the sagittal direction, pleaserefer to FIG. 9C for the field curvature on the tangential direction,and please refer to FIG. 9D for the distortion. The components in thisembodiment are similar to those in the first embodiment, but the opticaldata such as the curvature radius, the lens thickness, the asphericsurface or the back focal length in this embodiment are different fromthe optical data in the first embodiment. Besides, in this embodiment,the first lens element 10 has positive refracting power and the fourthlens element 40 has negative refracting power.

The optical data of the second embodiment of the optical imaging lensare shown in FIG. 22 while the aspheric surface data are shown in FIG.23. In this embodiment, image height=1.500 mm; EFL=2.274 mm; HFOV=32.831degrees; TTL=3.328 mm; Fno=1.5. In particular, 1. the longitudinalspherical aberration and the distortion of the optical imaging lens inthis embodiment are better than those of the optical imaging lens in thefirst embodiment, and 2. the fabrication of this embodiment is easierthan that of the first embodiment so the yield is better.

Third Embodiment

Please refer to FIG. 10 which illustrates the third embodiment of theoptical imaging lens 1 of the present invention. Please refer to FIG.11A for the longitudinal spherical aberration on the image plane 71 ofthe third embodiment; please refer to FIG. 11B for the field curvatureon the sagittal direction; please refer to FIG. 11C for the fieldcurvature on the tangential direction; and please refer to FIG. 11D forthe distortion. The components in this embodiment are similar to thosein the first embodiment, but the optical data such as the curvatureradius, the lens thickness, the aspheric surface or the back focallength in this embodiment are different from the optical data in thefirst embodiment. Besides, in this embodiment, the first lens element 10has positive refracting power, the periphery region 17 of the image-sidesurface 12 facing toward the image side 3 of the first lens element 10is convex, the periphery region 24 of the object-side surface 21 facingtoward the object side 2 of the second lens element 20 is concave, theoptical axis region 26 of the image-side surface 22 facing toward theimage side 3 of the second lens element 20 is concave and the fourthlens element 40 has negative refracting power.

The optical data of the third embodiment of the optical imaging lens areshown in FIG. 24 while the aspheric surface data are shown in FIG. 25.In this embodiment, image height=1.500 mm; EFL=2.554 mm; HFOV=30.000degrees; TTL=3.743 mm; Fno=1.5. In particular, the imaging quality ofthe optical imaging lens in this embodiment is better than that of theoptical imaging lens in the first embodiment.

Fourth Embodiment

Please refer to FIG. 12 which illustrates the fourth embodiment of theoptical imaging lens 1 of the present invention. Please refer to FIG.13A for the longitudinal spherical aberration on the image plane 71 ofthe fourth embodiment; please refer to FIG. 13B for the field curvatureon the sagittal direction; please refer to FIG. 13C for the fieldcurvature on the tangential direction; and please refer to FIG. 13D forthe distortion. The components in this embodiment are similar to thosein the first embodiment, but the optical data such as the curvatureradius, the lens thickness, the aspheric surface or the back focallength in this embodiment are different from the optical data in thefirst embodiment. Besides, in this embodiment, the first lens element 10has positive refracting power, the periphery region 37 of the image-sidesurface 32 facing toward the image side 3 of the third lens element 30is concave and the fourth lens element 40 has negative refracting power.There is a filter 70 disposed between the fourth lens element 40 and theimage plane 71 in the fourth embodiment and the filter 70 may be coatedwith a film which exclusively allow IR to pass through.

The optical data of the fourth embodiment of the optical imaging lensare shown in FIG. 26 while the aspheric surface data are shown in FIG.27. In this embodiment, image height=1.977 mm; EFL=2.498 mm; HFOV=35.043degrees; TTL=3.628 mm; Fno=1.29. In particular, 1. the Fno of theoptical imaging lens in this embodiment is smaller than that of theoptical imaging lens in the first embodiment, 2. the longitudinalspherical aberration of the optical imaging lens in this embodiment isbetter than that of the optical imaging lens in the first embodiment.

Fifth Embodiment

Please refer to FIG. 14 which illustrates the fifth embodiment of theoptical imaging lens 1 of the present invention. Please refer to FIG.15A for the longitudinal spherical aberration on the image plane 71 ofthe fifth embodiment; please refer to FIG. 15B for the field curvatureon the sagittal direction; please refer to FIG. 15C for the fieldcurvature on the tangential direction, and please refer to FIG. 15D forthe distortion. The components in this embodiment are similar to thosein the first embodiment, but the optical data such as the curvatureradius, the lens thickness, the aspheric surface or the back focallength in this embodiment are different from the optical data in thefirst embodiment. Besides, in this embodiment, the first lens element 10has positive refracting power, the periphery region 34 of theobject-side surface 31 facing toward the object side 2 of the third lenselement 30 is convex, the periphery region 37 of the image-side surface32 facing toward the image side 3 of the third lens element 30 isconcave and the fourth lens element 40 has negative refracting power.

The optical data of the fifth embodiment of the optical imaging lens areshown in FIG. 28 while the aspheric surface data are shown in FIG. 29.In this embodiment, image height=1.500 mm; EFL=2.170 mm; HFOV=34.255degrees; TTL=3.900 mm; Fno=1.25. In particular, 1. the Fno of theoptical imaging lens in this embodiment is smaller than that of theoptical imaging lens in the first embodiment, 2. the longitudinalspherical aberration and the distortion of the optical imaging lens inthis embodiment are better than those of the optical imaging lens in thefirst embodiment.

Sixth Embodiment

Please refer to FIG. 16 which illustrates the sixth embodiment of theoptical imaging lens 1 of the present invention. Please refer to FIG.17A for the longitudinal spherical aberration on the image plane 71 ofthe sixth embodiment; please refer to FIG. 17B for the field curvatureon the sagittal direction; please refer to FIG. 17C for the fieldcurvature on the tangential direction, and please refer to FIG. 17D forthe distortion. The components in this embodiment are similar to thosein the first embodiment, but the optical data such as the curvatureradius, the lens thickness, the aspheric surface or the back focallength in this embodiment are different from the optical data in thefirst embodiment. Besides, in this embodiment, the first lens element 10has positive refracting power, the periphery region 17 of the image-sidesurface 12 facing toward the image side 3 of the first lens element 10is convex, the periphery region 24 of the object-side surface 21 facingtoward the object side 2 of the second lens element 20 is concave, theperiphery region 37 of the image-side surface 32 facing toward the imageside 3 of the third lens element 30 is concave and the fourth lenselement 40 has negative refracting power.

The optical data of the sixth embodiment of the optical imaging lens areshown in FIG. 30 while the aspheric surface data are shown in FIG. 31.In this embodiment, image height=1.500 mm; EFL=2.134 mm; HFOV=33.397degrees; TTL=3.318 mm; Fno=1.00. In particular, 1. the Fno of theoptical imaging lens in this embodiment is smaller than that of theoptical imaging lens in the first embodiment, 2. the distortion of theoptical imaging lens in this embodiment is better than that of theoptical imaging lens in the first embodiment.

Seventh Embodiment

Please refer to FIG. 18 which illustrates the seventh embodiment of theoptical imaging lens 1 of the present invention. Please refer to FIG.19A for the longitudinal spherical aberration on the image plane 71 ofthe seventh embodiment; please refer to FIG. 19B for the field curvatureon the sagittal direction; please refer to FIG. 19C for the fieldcurvature on the tangential direction, and please refer to FIG. 19D forthe distortion. The components in this embodiment are similar to thosein the first embodiment, but the optical data such as the curvatureradius, the lens thickness, the aspheric surface or the back focallength in this embodiment are different from the optical data in thefirst embodiment. Besides, in this embodiment, the first lens element 10has positive refracting power, the periphery region 24 of theobject-side surface 21 facing toward the object side 2 of the secondlens element 20 is concave and the periphery region 34 of theobject-side surface 31 facing toward the object side 2 of the third lenselement 30 is convex.

The optical data of the seventh embodiment of the optical imaging lensare shown in FIG. 32 while the aspheric surface data are shown in FIG.33. In this embodiment, image height=1.500 mm; EFL=2.162 mm; HFOV=32.555degrees; TTL=3.545 mm; Fno=0.96. In particular, 1. the Fno of theoptical imaging lens in this embodiment is smaller than that of theoptical imaging lens in the first embodiment, 2. the imaging quality ofthe optical imaging lens in this embodiment is better than that of theoptical imaging lens in the first embodiment, 3. the fabrication of thisembodiment is easier than that of the first embodiment so the yield isbetter.

Some important ratios in each embodiment are shown in FIG. 34 and inFIG. 35.

The applicant found that by the following designs matched with eachother, the lens configuration in the embodiments of the presentinvention has the features and corresponding advantages:

1. The optical-axis region of the image-side surface of the first lenselement is designed to be concave, the periphery region of theimage-side surface of the second lens element is convex, the third lenshas positive refracting power and the optical-axis region of theobject-side surface of the fourth lens element is designed to be convex.It effectively increases the luminous flux of the total optical imaginglens system to simultaneously have good imaging quality.

By controlling ν2≤30.000 to go with (ν1+ν3+ν4)≤120.000, it helps tocorrect the chromatic aberration of the entire optical system. Theselection of the above-mentioned materials facilitates the purpose ofthe reduction of the length of the optical system due to the higherrefractive index. ν2 is preferably 20.000≤ν2≤30.000 and (ν1+ν3+ν4) ispreferably 60.000≤(ν1+ν3+ν4)≤120.000.

In addition, it is further discovered that there are some better ratioranges for different optical data according to the above variousimportant ratios. Better optical ratio ranges help the designers todesign a better optical performance and an effectively reduce length ofa practically possible optical imaging lens set:

To diminish the total length of the optical imaging lens, to ensure goodimaging quality and to take the easiness of the fabrication of theoptical imaging lens into consideration, the embodiments of the presentinvention proposes the solution to reduce the lens thickness and airgaps between adjacent lens elements. The following conditions help theoptical imaging lens have better arrangement:

1) ALT/BFL≥1.200, the preferable range is 1.200≤ALT/BFL≤2.700;

2) AAG/G23≤2.200, the preferable range is 1.000≤AAG/G23≤2.200;

3) EFL/(T1+T3)≤3.500, the preferable range is 2.000≤EFL/(T1+T3)≤3.500;

4) (T2+T3)/T1≥1.800, the preferable range is 1.800≤(T2+T3)/T1≤3.300;

5) (T3+T4)/(G23+G34)≤3.500, the preferable range is0.600≤(T3+T4)/(G23+G34)≤3.500;

6) (T1+T2)/(G12+G23)≤2.800, the preferable range is0.700≤(T1+T2)/(G12+G23)≤2.800;

7) BFL/(G34+T4)≤3.100, the preferable range is 1.000≤BFL/(G34+T4)≤3.100;

8) TL/(T1+G12)≥3.200, the preferable range is 3.200≤TL/(T1+G12)≤6.800;

9) EFL/AAG≤3.900, the preferable range is 1.900≤EFL/AAG≤3.900;

10) TTL/(T3+T4)≥3.800, the preferable range is 3.800≤TTL/(T3+T4)≤5.500;

11) ALT/T2≤4.800, the preferable range is 2.500≤ALT/T2≤4.800;

12) (T4+BFL)/T3≤4.500, the preferable range is 2.500≤(T4+BFL)/T3≤4.500;

13) T2/T1≥1.000, the preferable range is 1.000≤T2/T1≤2.000;

14) ALT/AAG≤4.500, the preferable range is 1.500≤ALT/AAG≤4.500;

15) TL/BFL≥1.800, the preferable range is 1.800≤TL/BFL≤3.500;

16) (T2+T3+T4)/T1≥2.500, the preferable range is2.500≤(T2+T3+T4)/T1≤4.500;

17) (T1+T3+T4)/T2≤3.500, the preferable range is1.500≤(T1+T3+T4)/T2≤3.500;

18) EFL/(T2+G23)≤3.000, the preferable range is1.500≤EFL/(T2+G23)≤3.000;

19) ALT/T1≥3.500, the preferable range is 3.500≤ALT/T1≤5.500.

In the light of the unpredictability of the optical imaging lens, thepresent invention suggests the above principles to have a shorter totallength of the optical imaging lens, a larger aperture available, betterimaging quality or a better fabrication yield to overcome the drawbacksof prior art.

In addition to the above ratios, one or more conditional formulae may beoptionally combined to be used in the embodiments of the presentinvention and the present invention is not limit to this. The curvaturesof each lens element or multiple lens elements may be fine-tuned toresult in more fine structures to enhance the performance or theresolution. The above limitations may be properly combined in theembodiments without causing inconsistency.

The maximum and minimum numeral values derived from the combinations ofthe optical parameters disclosed in the embodiments of the invention mayall be applicable and enable people skill in the pertinent art toimplement the invention.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. An optical imaging lens, from an object side toan image side in order along an optical axis comprising: a first lenselement, a second lens element, a third lens element and a fourth lenselement, the first lens element to the fourth lens element each has anobject-side surface facing toward the object side to allow imaging raysto pass through as well as an image-side surface facing toward the imageside to allow the imaging rays to pass through, wherein: the first lenselement has positive refracting power; an optical-axis region of theobject-side surface of the second lens element is convex; a peripheryregion of the object-side surface of the second lens element is convex;an optical-axis region of the image-side surface of the second lenselement is convex; the lens elements having refracting power included bythe optical imaging lens are only the four lens elements describedabove; wherein, ν1 is an Abbe number of the first lens element, ν2 is anAbbe number of the second lens element and ν3 is an Abbe number of thethird lens element, and the optical imaging lens satisfies therelationship: 61.119≤ν1+ν2+ν3≤96.733.
 2. The optical imaging lens ofclaim 1, wherein AAG is a sum of three air gaps from the first lenselement to the fourth lens element along the optical axis and G23 is anair gap between the second lens element and the third lens element alongthe optical axis, and the optical imaging lens satisfies therelationship: AAG/G23≤2.200.
 3. The optical imaging lens of claim 1,wherein T3 is a thickness of the third lens element along the opticalaxis, T4 is a thickness of the fourth lens element along the opticalaxis, G23 is an air gap between the second lens element and the thirdlens element along the optical axis and G34 is an air gap between thethird lens element and the fourth lens element along the optical axis,and the optical imaging lens satisfies the relationship:(T3+T4)/(G23+G34)≤3.500.
 4. The optical imaging lens of claim 1, whereinEFL is an effective focal length of the optical imaging lens and BFL isa distance from the image-side surface of the fourth lens element to animage plane along the optical axis, and the optical imaging lenssatisfies the relationship: 1.911≤EFL/BFL≤2.791.
 5. The optical imaginglens of claim 1, wherein T3 is a thickness of the third lens elementalong the optical axis, G12 is an air gap between the first lens elementand the second lens element along the optical axis and G23 is an air gapbetween the second lens element and the third lens element along theoptical axis, and the optical imaging lens satisfies the relationship:1.183≤(G12+G23)/T3≤2.725.
 6. The optical imaging lens of claim 1,wherein T2 is a thickness of the second lens element along the opticalaxis, T3 is a thickness of the third lens element along the opticalaxis, G23 is an air gap between the second lens element and the thirdlens element along the optical axis and G34 is an air gap between thethird lens element and the fourth lens element along the optical axis,and the optical imaging lens satisfies the relationship:1.551≤(T2+T3)/(G23+G34)≤2.989.
 7. The optical imaging lens of claim 1,wherein EFL is an effective focal length of the optical imaging lens, T1is a thickness of the first lens element along the optical axis and T3is a thickness of the third lens element along the optical axis, and theoptical imaging lens satisfies the relationship:2.424≤EFL/(T1+T3)≤3.501.
 8. The optical imaging lens of claim 1, whereinTL is a distance from the object-side surface of the first lens elementto the image-side surface of the fourth lens element along the opticalaxis, G34 is an air gap between the third lens element and the fourthlens element along the optical axis and T4 is a thickness of the fourthlens element along the optical axis, and the optical imaging lenssatisfies the relationship: 4.499≤TL/(G34+T4)≤6.584.
 9. The opticalimaging lens of claim 1, wherein BFL is a distance from the image-sidesurface of the fourth lens element to an image plane along the opticalaxis, AAG is a sum of three air gaps from the first lens element to thefourth lens element along the optical axis and ALT is a sum of thicknessof all the four lens elements along the optical axis, and the opticalimaging lens satisfies the relationship: 2.607≤(BFL+ALT)/AAG≤4.740. 10.The optical imaging lens of claim 1, wherein TTL is a distance from theobject-side surface of the first lens element to an image plane alongthe optical axis, T1 is a thickness of the first lens element along theoptical axis and T3 is a thickness of the third lens element along theoptical axis, and the optical imaging lens satisfies the relationship:3.775≤TTL/(T1+T3)≤5.081.
 11. An optical imaging lens, from an objectside to an image side in order along an optical axis comprising: a firstlens element, a second lens element, a third lens element and a fourthlens element, the first lens element to the fourth lens element each hasan object-side surface facing toward the object side to allow imagingrays to pass through as well as an image-side surface facing toward theimage side to allow the imaging rays to pass through, wherein: the firstlens element has positive refracting power; an optical-axis region ofthe object-side surface of the second lens element is convex; anoptical-axis region of the image-side surface of the second lens elementis convex; the lens elements having refracting power included by theoptical imaging lens are only the four lens elements described above;wherein, EFL is an effective focal length of the optical imaging lens,T2 is a thickness of the second lens element along the optical axis, G23is an air gap between the second lens element and the third lens elementalong the optical axis, ν1 is an Abbe number of the first lens element,ν2 is an Abbe number of the second lens element and ν3 is an Abbe numberof the third lens element, and the optical imaging lens satisfies therelationship: 61.119≤ν1+ν2+ν3≤96.733 and EFL/(T2+G23)≤3.000.
 12. Theoptical imaging lens of claim 11, wherein TTL is a distance from theobject-side surface of the first lens element to an image plane alongthe optical axis, T3 is a thickness of the third lens element along theoptical axis and T4 is a thickness of the fourth lens element along theoptical axis, and the optical imaging lens satisfies the relationship:TTL/(T3+T4)≥3.800.
 13. The optical imaging lens of claim 11, wherein T4is a thickness of the fourth lens element along the optical axis and G12is an air gap between the first lens element and the second lens elementalong the optical axis, and the optical imaging lens satisfies therelationship: 1.024≤(G12+G23)/T4≤2.318.
 14. The optical imaging lens ofclaim 11, wherein T4 is a thickness of the fourth lens element along theoptical axis, and the optical imaging lens satisfies the relationship:4.280≤EFL/T4≤7.854.
 15. The optical imaging lens of claim 11, whereinALT is a sum of thickness of all the four lens elements along theoptical axis, T4 is a thickness of the fourth lens element along theoptical axis, and G34 is an air gap between the third lens element andthe fourth lens element along the optical axis, and the optical imaginglens satisfies the relationship: 3.481≤ALT/(G34+T4)≤4.371.
 16. Theoptical imaging lens of claim 11, wherein TL is a distance from theobject-side surface of the first lens element to the image-side surfaceof the fourth lens element along the optical axis and AAG is a sum ofthree air gaps from the first lens element to the fourth lens elementalong the optical axis, and the optical imaging lens satisfies therelationship: 2.802≤TL/AAG≤4.420.
 17. The optical imaging lens of claim11, wherein AAG is a sum of three air gaps from the first lens elementto the fourth lens element along the optical axis, T3 is a thickness ofthe third lens element along the optical axis and G34 is an air gapbetween the third lens element and the fourth lens element along theoptical axis, and the optical imaging lens satisfies the relationship:1.129≤AAG/(T3+G34)≤2.604.
 18. The optical imaging lens of claim 11,wherein T1 is a thickness of the first lens element along the opticalaxis and T3 is a thickness of the third lens element along the opticalaxis, and the optical imaging lens satisfies the relationship:1.193≤(T1+T3)/T2≤1.995.
 19. The optical imaging lens of claim 11,wherein TTL is a distance from the object-side surface of the first lenselement to an image plane along the optical axis and AAG is a sum ofthree air gaps from the first lens element to the fourth lens elementalong the optical axis, and the optical imaging lens satisfies therelationship: 3.607≤TTL/AAG≤5.740.
 20. The optical imaging lens of claim11, wherein TTL is a distance from the object-side surface of the firstlens element to an image plane along the optical axis and T1 is athickness of the first lens element along the optical axis, and theoptical imaging lens satisfies the relationship:2.772≤TTL/(T1+T2)≤4.058.